Resistive film bleeder resistor for use in an branch circuit

ABSTRACT

A bleeder resistor used in a branch circuit for dividing a high frequency electric power into a plurality of parts, in which three electrodes are disposed at vertex corners of a regular triangle on an insulative plate, and in which a resistive film is deposited on the surface of the insulative plate so as to be connected to all the three electrodes so that a resistance between any two of the three electrodes is substantially equal to a desired value in a wide frequency range.

United States Patent Ozawa et al. 1 Oct. 24, 1972 [54] RESISTIVE FILM BLEEDER RESISTOR [56] References Cited OR SE IN AN BRANCH CIR UIT F U C UNITED STATES PATENTS [72] Inventors: Syulchl Ozawa; Noboru Tomimura,

both f Tokyo japan 2,231,332 12/ [Gee .5..333/8l 1 t 731 Assignee: lwasaki Tsushinld Kabushiki Kaisha I e 33/81 A SF t Electric Primary Examiner-Paul L. Gensler 0 apan Attorney-Robert F. Burns and Emmanuel J. Lobato [22] Filed: Aug. 24, 1970 [2]] Appl. No.: 66,292 [57] ABSTRACT A bleeder resistor used in a branch circuit for dividing a high frequency electric power into a plurality of [30] Foreign Application Priority parts, in which three electrodes are disposed at vertex Allg- 25! 1969 Japan -44/66626 corners of a regular triangle on an insulative plate, and in which a resistive film is deposited on the surface of US. Cl. R, A, the insulative plate so as to be eonnegted to the 333/325 three electrodes so that a resistance between any two [5 1] Int. Cl. J10!!! 1/22, HOlc 7/00 of the three electrodes is substantiauy equal to a [58] Field of Search ..333/6, 8, 22, 81. 81 A, 9', desired value in a wide frequency range 5 Claims, 13 Drawing Figures RES/5 r/v FILM 18 X 5-Ez. ECTRODE 19 INSULATIVE g PLATE r I l r 7 3 l/ C] i 2 "63" c3 I I e ELE C TROOE ELECTRODE PITENIEMHM m 3.701. 056

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Hg. 4 15m 19 l RESISTIVE FILM BLEEDER RESISTOR FOR USE IN AN BRANCH CIRCUIT This invention relates to a bleeder resistor used in a branch circuit for dividing a high frequency electric power into a plurality of parts.

The bleeder resistor of this type has an input terminal matching with an input impedance and a plurality of output terminals so that an input power applied to the input terminal is divided into a plurality of parts, which are derived from the output terminals respectively. However, conventional bleeder resistors have such disadvantages as small allowable input power, structural mis-matching of impedance, and difficulty of miniaturization.

An object of this invention is to provide a bleeder resistor capable of readily performing impedance matching, and capable of being formed into a small size but having a relatively large allowable input power.

In a bleeder resistor of this invention used in a branch circuit for dividing a high frequency electric power into a plurality of parts, three electrodes are disposed, in accordance with the principle of this invention, at vertex corners of a regular triangle on an insulative plate. A resistive film is deposited on the surface of the insulative plate so as to be connected to all of the three electrodes so that a resistance between any two of the three electrodes is substantially equal to a desired value in a wide frequency range. The insulative plate may be a triangular plate whose vertex corners are truncated so as to form a hexagon. The resistive film may have a pattern similar to the pattern of the insulative plate. If necessary, at least a part of the resistive film may be removed to adjust the resistance between any two of the three electrodes.

The invention will be better understood from the following more detailed discussion taken in conjunction with the accompanying drawings, in which:

FIGS. I, 2 and 3 are schematic sections illustrating the arrangement of conventional high-frequency branch circuits using bleeder resistors;

FIG. 4 is a plan view illustrating an embodiment of the bleeder resistor of this invention;

FIG. 5 is a right-side view of the embodiment shown in FIG. 4;

FIG. 6 is a plan view partially in section illustrating the main part of a high-frequency branch circuit using the embodiment shown in FIG. 4;

FIG. 7 is a section along a line 3-5 shown in FIG. 6;

FIG. 8 is a plan view illustrating another embodiment of this invention;

FIG. 9 is a right-side view of the embodiment shown in FIG. 8;

FIG. 10 is a plan view partially in section illustrating the main part of a high-frequency branch circuit using the embodiment shown in FIG. 8; and

FIGS. 11, I2 and 13 are plan views each illustrating another embodiment of this invention.

To make differences between this invention and conventional art clear, examples of conventional highfrequency branch circuits will first be described with reference to FIGS. I, 2 and 3. In an example shown in FIG. I, cylindrical rod resistors l, 2 and 3 are arranged in a T-type." On the other hand, cylindrical rod resistors 6, 7 and 8 are arranged in a Y-type" in an example shown in FIG. 2, while cylindrical rod resistors 11, 12 and 13 are arranged in a A-type" in an example shown in FIG. 3. In the examples shown in FIGS. 1 and 2, if an input signal is applied to an input terminal 4 or 9, a power larger than power applied across the resistors l and 3) or (7 and 8) is applied to a resistor 2 or 6 connected to the input terminal 4 or 9. Accordingly, the allowable input power of this high-frequency branch circuit is limited by a relatively small allowable power of the rod resistor 2 or 6. Moreover, mismatching of impedance is structurally caused at a junction 5 or 10. In the example shown in FIG. 3. if an input signal of the same power as the input signal applied to the terminal 4 or 9 is applied to an input terminal 14, the power of this input signal is divided into two parts by the resistors 11 and 13. Accordingly, the allowable power of this branch circuit is larger than the example shown in FIG. 1 and 2 since a power smaller than the power applied to the resistor 2 or 4 is applied to the resistors 11 and 13. However, since electric fields generated by the two divided currents flowing respectively through the resistors 11 and 13 interfere with each other, impedance matching within all the active frequency range is very difficult due to complicated modes of the electric fields. Moreover, miniturization of the above mentioned examples shown in FIGS. 1, 2 and 3 is difficult.

With reference to FIGS. 4 and 5 an embodiment of this invention comprises three electrodes 15, 16 and 17 disposed at vertex comers of a regular triangle on an insulative plate 19, and a triangular, resistive film 18 is deposited on at least one surface of the insulative plate 19 so as to be connected to the electrodes 15, 16 and 17 at the vertex comers of the triangular resistive film 18 whose vertex comers are cut off perpendicularly to lines bisecting the angles of the triangle so as to form a hexagon having alternate long and short sides. Each of the electrodes 15,16 and 17 matches respectively one of the short sides of the hexagon. In this case, this resistive film 18 is deposited on the insulative plate 19 so that the resistance of a unit area (i.e.; area resistance) is constant at any place of the film 18. In this construction, capacitances (3,, C and C provided by dielectric of the resistive film l8 exist among the three electrodes 15, 16 and 17, while capacitances C C and C provided by dielectric of the insulative plate 19 exist also among the three electrodes l5, l6 and 17. These capacitances C,, C C C C and C are equivalently parallel with the resistive film 18. In other words, the capacitances C and C exist between the electrodes 15 and 16, the capacitances C and C exist between the electrodes 16 and 17, and the capacitances C and C exist between the electrodes 17 and 15. The equivalent circuit 20 of the unit area is shown in FIG. 4. In this case, since the area resistance is constant at any place of the resistive film 18, resistances r, and r are equal to each other. Moreover. a first resultant value of the resistance r and a capacitance C, is equal to a second resultant value of the resistance r and a capacitance C Accordingly, a division ratio r,/r relating to the resistances r. and r is equal to a division ratio C /C relating to the capacitances C and C These division ratios have no connection with the frequency of the input signal. This principle can be expanded to the whole area of the resistive film 18. Moreover, since the three electrodes 15, 16 and 17 are disposed at the vertex corners of a regular triangular, the capacitances C1, C2 and C are equal to one another while the capacitances C C and C are equal to one another. Accordingly, a desired division ratio can be always obtained.

The bleeder resistor shown in FIGS. 4 and 5 is employed to form a branch circuit as shown in FIGS. 6 and 7. Impedance-matching can be readily performed by adjusting the space W between two screwed covers 22 and 23 which are screwed into openings in an outer conductor 2!.

To fabricate the bleeder resistor of this invention at a low cost, electrodes 25, 26 and 27 and a resistive film 28 may be provided on an orbicular plate 24 as shown in FIGS. 8 and 9. in this case, capacitances C C C and C provided by dielectric of an insulative material (e.g.; alumina) and the air gap exist, as shown in FIG. 10, between the electrodes 25 and an outer conductor 29 and between the resistive film 28 and the outer conductor 29, so that the attenuation factor of this bleeder resistor increases while mismatching of impedance will not be negligible. In view of the situation, edges of the insulative plate 19 of the embodiment shown in FIG. 4 are out along the triangular, resistive film 18 so as to form a hexagon similar to the hexagon of the film 18, so that capacitances between outer conductor 21 and a block of the resistive film 18 and the electrodes l5, l6 and 17 are reduced. However, if the bleeder resistor is employed to form a branch circuit operating in a low frequency range, the embodiment shown in FIGS. 8, 9 and 10 is suitable for this purpose.

In order to make resistances between electrodes and 16, between electrodes 16 and I7, and between electrodes 17 and 15 equal to one another and to make the area resistance uniform over the whole area of the resistive film 18 in the embodiment shown in FIG. 4, the resistance of the resistive film 18 is regulated by depositing the resistive film 18 at a uniform thickness and by precise design of respective distances between adjacent electrodes (15 and l6), (l6 and 17) and (l7 and l5). To meet with these requirements, long adjusting time, highly precise installations and skilful techniques are necessary. However, if a part 35 or 37 or parts 31, 32 and 33 of a resistive film 34, 36 or 30 is or are removed as shown in FIGS. ll, 12 and 13, the above-mentioned requirements can be readily satisfied. ln this case, if respective differences among capacitances C C and C among C,,,, C and C and among C C and C are small, the division factor of each of the embodiments shown in FIGS. 11, 12 and 13 is constant to the extent of a limited frequency since effect of the differences is small with the limited frequency.

What we claim is: l. A bleeder resistor, comprising: an insulative plate, three like electrodes symmetrically disposed at vertex corners of a regular triangle on the insulative plate and having equal edges each perpendicular to a corresponding one of lines bisecting the respective angles of the regular triangle, at least one regular triangular resistive film deposited on the surface of the insulative plate and having truncated vertex corners respectively matched with said edges of the three electrodes, so that the resistance between any two of the three electrodes is substantially equal and corresponds to a desired val einawide fre uenc ran e. 2. A lileeder resistoi accoi ding to claim 1, in which the insulative plate is an orbicular insulative plate.

3. A bleeder resistor according to claim 1, in which said electrodes are rectangular with longer central axes perpendicular respectively to said lines bisecting the angles of said triangle.

4. A bleeder resistor according to claim l, in which the insulative plate is a triangular plate similar to said regular triangular resistive film and having sides parallel to sides of said triangular resistive film and truncated vertex corners.

5. A bleeder resistor according to claim 4, in which at least a part of the resistive film is removed to adjust the resistance between any two of the three electrodes. 

1. A bleeder resistor, comprising: an insulative plate, three like electrodes symmetrically disposed at vertex corners of a regular triangle on the insulative plate and having equal edges each perpendicular to a corresponding one of lines bisecting the respective angles of the regular triangle, at least one regular triangular resistive film deposited on the surface of the insulative plate and having truncated vertex corners respectively matched with said edges of the three electrodes, so that the resistance between any two of the three electrodes is substantially equal and corresponds to a desired value in a wide frequency range.
 2. A bleeder resistor according to claim 1, in which the insulative plate is an orbicular insulative plate.
 3. A bleeder resistor according to claim 1, in which said electrodes are rectangular with longer central axes perpendicular respectively to said lines bisecting the angles of said triangle.
 4. A bLeeder resistor according to claim 1, in which the insulative plate is a triangular plate similar to said regular triangular resistive film and having sides parallel to sides of said triangular resistive film and truncated vertex corners.
 5. A bleeder resistor according to claim 4, in which at least a part of the resistive film is removed to adjust the resistance between any two of the three electrodes. 